J.P. Morgan Chase & Co.'s board delivered a strong endorsement of Chief Executive James Dimon, boosting his pay 74% for a year in which the nation's largest bank agreed to more than $20 billion in legal payouts and suffered its first quarterly loss in nine years.

The increase for 2013, to $20 million, restored most of the pay cut Mr. Dimon took the previous year, when the board held him accountable for a trading fiasco that...